Our results show for the first time that Abi1 is overexpressed at the invasive edge of colorectal carcinomas that display an aggressive phenotype; furthermore, phosphorylated Abi1 as well as Cortactin localize to foci of matrix degradation in the tumour cell periphery, while treatment with STI571 leads to a depletion of Y435-phosphorylated Abi1 in this compartment and suppresses tumour cell attachment to fibronectin as well as ECM degradation and tumour cell invasion in vitro. This evidence concerns the gene ABI1 and colorectal carcinoma.